Experimental Study On Flow-induced Vibration Characteristics Of Fast Reactor Fuel Assembly

Fast reactor components are the important part of fast reactor core.Fast reactor components generally consist of pins,hexagonal bushings,fuel rod bundles,and operating head.The significant difference from pressurized water reactor components is the addition of hexagonal bushings.,The fuel assembly has its own flow path.Its integrity is very important for the normal operation of the entire primary circuit system and the entire fast neutron reactor.Fast reactor components run with the reactor for a long time,the flow-induced vibration behavior may cause fatigue and wear of the structural components of the module,which in turn will cause component structure failure,even fatigue fracture and fuel rod sealing failure,so it is necessary to conduct fluid induced vibration test on the component;At present,the flow-induced vibration experiments of the entire core are difficult to implement.and single components are the mainstream research;In accordance with the design requirements of fast reactor components,the lower pins of the module are directly socketed in the small grid joint box.When conducting fluid-induced vibration experiments,there are constraint on the upper boss of the module.Such constraints will change with the various vibration behaviors of the module in the stack,the gap will increase or decrease to collide with each other.This variety of upper support mode will have a certain effect on the flow-induced vibration characteristics of the module.At present,the existing research methods are simulated by adding a fixed gap.From the perspective of engineering design,the research using a fixed gap may not be representative of the actual complex vibration behavior in the reactor.In this paper,the influences of the two methods,with upper gap constraint and no gap constraint on the flow-induced vibration characteristics of the module are studied,which provides some references for the subsequent research on the flow-induced vibration of fast reactor components.In this paper,the influence of the upper boss constraint between components on the flow-induced vibration response of the components is studied experimentally,and the response behavior of the components is evaluated.The experiment includes the measurement of the natural frequency of the module,three bending modes of the module are obtained,providing certain reference data for the flow-induced vibration experiment.The main body of the experiment is the flow-induced vibration experiment.By collecting the acceleration and strain response of the component at different positions,we obtain the vibration displacement,amplitude mean square value and strain peak value of the module,and obtain the distribution of excitation energy on the frequency spectrum by fast Fourier transform.By comparing the results of the constraint on the upper part and without the constraint on the upper part,it is found that the maximum displacement value of the component without the upper component constraint is slightly larger in the rated flow(11.094 m3/h).This paper provides technical data for the design of the module structure in engineering,and has reference value for future experimental research on flow-induced vibration of fuel assemblies in fast reactors.